Mickelson's challenge was disrupted by a triple bogey six at the short fourth and he was never able to get on terms in search of his fourth Masters crown as he finished with a level-par 72.

Hanson also struggled early in his round before a late rally.

Up ahead, world No. 3 Westwood, once again immaculate from tee to green, carded a four-under 68 to set the clubhouse pace in search of his first major crown and was joined on that mark by local favorite Kuchar.

But Oosthuizen and Watson kept their nerve, parring both the 17th and 18th to stay locked together at 10 under par to go into the extra holes.

Two of the pre-tournament favorites, Tiger Woods and Northern Ireland's world No. 2 Rory McIlroy, finished tied together at five over, 15 shots adrift after final rounds of 74 and 76 respectively.